LEDs (Light Emitting Diodes) are a promising replacement to traditional fluorescent and incandescent lighting due to superior characteristics such as low energy consumption, long operation life, compact size, fast response time, and mercury-free components. A popular white light LED configuration is the phosphor-converted LED (pc-LED), where blue LED chips are covered with yellow phosphor powders to convert the blue light into white light. This configuration has relatively low cost and has high conversion efficiency, compared to other typical white light LED technologies such as the RGB method and the ultraviolet LEDs with RGB phosphors method.
It is expected that a substantial portion of conventional incandescent and fluorescent lighting will be replaced by LEDs in the next 5-10 years. There are two major factors controlling the propagation of HB-LEDs (High Brightness LEDs) for SSL (Solid State Lighting) applications. One is optoelectronic efficacy and the other is the cost. Both factors are closely related to the packaging of LEDs. However, most conventional LED packaging methods require molds and peripheral components for either the phosphor coating or the lens forming, resulting in relative low throughput and high cost. In addition, thermal performance needs to be improved for high power LEDs. Therefore, a simplified yet more efficient packaging process is needed for LEDs so as to achieve low cost manufacture while delivering optimal optical and thermal performance.
FIG. 1 is an example of a sectional view of a conventional LED package 100. In this kind of package, an LED chip 113 is flip chip bonded by solder joints 115 to a flat silicon submount 117 including metal circuits (not shown) for electric connection between the LED chip 113 and the submount 117. The submount 117 with the LED chip 113 bonded together is then attached to a heat sink 101 by an adhesive 119. Further, the LED package 100 includes leads 107 which are held by a plastic body 105 and are wire bonded 103 to the silicon submount 117 to realize the electric connection. Then a lens (encapsulant) 111, which is fabricated in advance, covers the LED chip 113, wires 103 and the submount 117. The whole package is finally attached to the board 109 (e.g., a printed circuit board (PCB)) which performs electric signal distribution and heat dissipation.
The process of fabricating the LED package 100 shown in FIG. 1 suffers from high cost due to its complicated structure. Moreover, conventional LED dies are encapsulated individually, precluding the implementation of a mass production process that could potentially provide high yield with low cost.